The very definition of “perennial” brings up words like “persistent,” “enduring” and “resilient.” When we talk about resilient ag landscapes, we refer to green and living roots, an active microbial community, and collectively, the ability to endure and persist, or resiliency in the face of weather extremes.
So why don't we consider integrating perennial grasses into our annual cropping systems, and how can livestock be an integral part of the design?
Consider the benefits of an expanded rotation with cover crops — living roots to hold the soil, increased soil organic matter, and greater infiltration and water-holding capacity — and consider the advantage of having that cover crop growing year after year in a given field or part of a field.
Daren Redfearn, associate professor in UNL's agronomy and horticulture department, calls perennial grasses "woefully underutilized."
While perennials offer many of the same benefits as annual cover crops, Redfearn notes they function differently.
"Especially perennials, they have the highest biomass production, the greatest root mass production. They're adding more carbon and organic matter back to the soil. That's the biggest advantage. The second is root volume. They do a good job of holding soil in place and preventing erosion," he says. "You also only have to establish them one time. They're not quite as forgiving as annuals, but there are certain management practices that can speed up establishment."
Conventional wisdom says it takes three years to establish a stand of warm-season grasses. However, over the years, the USDA Agricultural Research Service in Nebraska has worked on breeding grasses that are easier to get started under a range of conditions. With good conditions and weed control, establishment in 15 to 18 months is quite common. This is because herbicide technology has improved over the last 20 years, making it more convenient and flexible to establish perennial grasses, possibly in a rotation system.
And while perennials are useful for permanent conservation structures like contour buffers, buffer strips or even prairie strips, Charles Francis, professor in UNL's agronomy and horticulture department, notes perennials aren't only useful for seeding in permanent conservation structures, they can also be planted in rotation with annual crops.
"One of the possibilities is a system that was common in the Pampas of Argentina for a couple of centuries, that involves rotating perennial pasture and grazing cattle with annual crops for three to four years," Francis says. "The system was quite sustainable at some level of yield, because the animals provided a lot of fertility and nutrients back to the land. There also weren't as many problems with pests."
"I think this type of rotation has real promise in the Great Plains, because with all the building on farmland and the amount of land we're losing — over 1 million acres a year in the U.S. — it doesn't take rocket science to figure out we'll have about half as much farmland per person by 2050 as we have today," Francis adds. "And with the need to produce 70% more food by then, we've got to do things differently. We'll be pushed for all kinds of reasons to increase production on marginal lands. We've got to do it in a smart way."
"Nobody has really bitten the bullet yet to look at that sort of system. But that's something we've had on the back burner, and we’ve turned it up at least to medium-term thinking about how we can approach it," Redfearn says. "I don't think you can include perennial grasses in a crop rotation without including livestock as well. You can't do one without the other."
"Nobody has really bitten the bullet yet to look at that sort of thing. But that's something we've got on the backburner. And the burner is turned up at least to medium thinking about how we can approach it," Redfearn says. "I don't think you can include perennial grasses in a crop rotation without including livestock as well. You can't do one without the other."
While livestock are necessary to realize the quickest return on investment from a perennial-annual rotation, Redfearn notes they also help build the soil and cycle nutrients quicker.
And rotating annual crops with perennial forages isn't completely foreign to Nebraska farmers.
"Growers in Nebraska have used alfalfa as a component in crop rotations in the past; it's not like we have never done anything like that," Redfearn notes. "But alfalfa has been managed more as a mechanically harvested crop than it has as a forage."
And while growers who have incorporated perennials into the landscape always have grazing livestock, the reverse is almost always true as well, Redfearn adds.
"Nobody seems to be doing this with just crops and cover crops. They've still got a perennial grass component they use. They may not use it all the time, but it's there," he says. "It's a fallback. You know those perennials have different productivity depending on the year, but they're out there every year."
This kind of creative thinking by farmers and university researchers will be essential in designing future systems, Francis says, noting a quote by former UNL vice chancellor and animal science professor Irv Omtvedt: “Business as usual is not adequate to meet future demands.”